Direct current control system



Dec. 16, 1952 M. BRACUTT DIRECT CURRENT CONTROL SYSTEM 4 Sheets-Sheet 2Filed March 18, 1950 5 .v n 3 t c P. 2 e m a o 2.. e V f T un N au T 3I. A 2 s e 2 n. u QH Q M e w ESC@ s 9 4 wnku M um M rxlL E T s Y s T mwm U w m M m m EQ2 m M w w uw m in D o 5 9 1 2 5 8 9 l 1.. .n o 6 .u 1|.M ,w l e a n d um@ Dec. 16; 1952 M. BRACUTT 2,622,239

DIRECT CURRENT CONTROL SYSTEM Filed March 18, 1950 4 Sheets-Sheet 4ATTORNEY Patented Dec. 16, 1952 DIRECT CURRENT CONTROL SYSTEM MichaelBracutt, East Orange, N. J., assigner, by mesne assignments, toReconstruction Finance Corporation, New York, N. Y., a corporation ofthe United States Application March 18, 1950, Serial No. 150,420

3 Claims. 1

This invention relates to control systems for reversing and/or varyingthe current supplied to a direct current load. More particularly theinvention relates to systems of the saturable reactor type for reversingand/or varying the magnitude of the current supplied to such a load.

The invention finds application in the control of the direction ofrotation and of the speed of a direct current motor of the ordinary typeand of given power rating from an alternating current source, by meansof a relatively small amount of power and without requiring moving partsor vacuum tubes between the control point and the motor.

An object of the invention is to provide control systems of the kindreferred to, which are particularly applicable to either single or polyphase power sources and which present a balanced load to such sources.

Another object is to provide a control circuit utilizing saturablereactors or magnetic ampliers of the self-saturating type forcontrolling the direction and magnitude of the current supplied to adirect current load energized from an A. C. circuit.

These and other objects and features or" the invention will beunderstood more clearly from the following detailed description inconnection with the accompanying drawings, in which:

Fig. 1 is a schematic diagram of an embodiment of the inventionillustrating its application as a D. C. motor reverser and speed controlcircuit energized from a single phase A. C. power source;

Fig. 2 is a characteristic curve of a saturable reactor employed in thecircuit of Fig. 1;

Fig. 3 is a diagram of a system similar to Fig. l, but adapted topresent a balanced load to the A. C. power source;

Fig. 4 is a diagram of a system energized by a polyphase power source;

Fig. 5 shows a modification of the polyphase connections of Fig. 4.

In Fig. 1, the D. C. motor I, having the magnetic iield II and armatureI2, has its field II connected to the rectifier I3, the rectier beingenergized by alternating current applied to the conductors I4 forexciting the eld II. The

armature I2 is energized through a load supply sla 22 and conductor I6.Also connected to the conductor I 5, in parallel with conductor I'I isthe conductor Il in series with the coil 23, rectiiiers 24 and 25, coil26 and conductor I6.

Coils 2I and 23 are saturable reactor load coils of the reactor ormagnetic amplifier A, having the D. C. input control coil 21 forcontrolling the degree of magnetic saturation in the ampliiier. Coils I8and 26 are saturable reactor load coils of the reactor or magneticamplier B, having the D. C. input control coil 28 for controlling thedegree of magnetic saturation in the amplifier. Ampliers A and B are ofthe well known self-saturating or self-excited type.

It will be seen that the paths traced over conductor I'I` includes twoarms in series, one arm including coil I8 and rectiiier I9, and theother arm including rectifier 2D and coil 2|, the junction between thesearms being connected to the lower terminal of armature I2. Similarly,the path over conductor I1 includes two arms in series, one armincluding coil 23 and rectifier 24, and the other arm includingrectifier 25 and coil 26, the junction between these arms beingconnected to the upper terminal of armature I2. It will also be seenthat all four of the rectiers I4, 20, 24 and 25 in the paths I1 and I1are similarly directed with respect to the parallel connection of thesepaths with conductors I5 and I6.

The D. C. control coils 2l and 28 are connected in series between theoutput terminals 29 and 30 of the double potentiometer control 3I whichserves as a reverser or speed control unit,` providing for manualcontrol of the motor I8. Control unit 3| has the diametrically oppositesliding contacts 32 and 33 rigidly coupled together mechanically, asindicated by the dotted line 34, but insulated electrically from eachother, and connected to any suitable source of direct current, such asrectier I3.

When the control 3l is positioned, as shown, with the sliders 32 and 33on the zero position, the terminals 29 and 30 are at the same potential,so that no current flows through the control coils 21 and 28 ofamplifiers A and B. Under this condition the flux in both amplifiers Aand B varies from 0 in Fig. 2 toward the point m on curve 30, and theresulting high impedance of reactor coils I8, 2l, 23, 26, opposes theflow of current through paths I'I and Il', and no current passes throughthe rectiers I9, 2t, 24 and 25 to the motor armature I2. Consequentlythe armature I2 remains without energization.

magnetization of reactor and will When sliders 32, 33 of controller 3iare rotated in one direction from the zero position, current begins toflow through D. C. coils 2 and 253, and as the rotation of the slidersis increased, the magnetization of reactors A and B passes through 5 thepoints m and n, respectively, where current begins to flow inappreciable quantity through reactor coils 2I and 23 in series with thearmature I2. Any further rotation of controller 3i in the samedirection, increases the armature current until the desired speed ofrotation of the armature is obtained in one direction. rThe direction ofcurrent ilow in the circuit o D. C. control coils 21 and 28 under theseconditions and the direction of the corresponding rectiiied pulsesthrough l5 reactor coils 2l and 23 and rectifiers and 2d, is indicatedby the full line arrows. It is thus possible to Vary the direction andamount of current ,passing through D. C. control coils 2 and 28 andthereby adjust the degree of magnetica 2O tion or saturation of reactorsA and Reactors A and i3 so connec are magnetised in opposite direc bycurrent through c s of other magnetization applied thereto.

Fig. 2 shows the cl: actei Stic curve of 'inagnetising current thrciv ocoils 2'! i? plotted against the magnet .un produced thereby in reactorsA and 'When reactor A is in gnetize-:l to the value m, where increaeation produces increasing the reactor E is oppositely rn n at the otherend ci the c ing magnetization produce of the reactor lt will be notedthat the rectified current through ce directieas produce trol currentthrough coil 2"?, t saturation of reactor A, and reducing the c.. ergyi0 required in coil to pass the desired curr-nt through coils 2i to themotor i2.

At the saine time, the magnetic B is .initially at the value n when apprent begins to icw through rectifier Any flow ci Y".nrent through coilsi3 be in a direction tendina, to

tain the reactor at i" h impeden-V fiow 0i current thro ctiiiers reactorA is transniitt ne ci In a similar manner, t controller otated in theopposite direction that just described, `until reactor A magnetized to avalue corresponding with pointJ n, Fig. 2, and reactor B is magnetisedto a value corresponding to the point m, reactor is reduced in impedanceas controller .il is adjusted to increase current through coils 27 and,while react r A is maintained at high impedance to prevent appreciablecurrent from passing through rectliiers 2li and 25 to the armature E2.Reactor B thus permits the rect-iiiers l Ei and 25'; to transmitrectified pulses to the armature ill in the direction indicated by the55 dotted arrows, thus causing the armature i2 to rotate in an oppositedirection from that pre-- viously described when react-or A was of .lowirnpedance. The speed of the ari.' ure in each case is controlled by theextent of rota .con ci' controller 70 3l from its zero position.

It will be understood that the control unit SI may be replaced byvarious other well known units, such as a push-pull electronic amplifierunit (not shown), adapted to provide an adjustable 75 4 and reversibledirect current of small value for control purposes.

Fig. 3 shows a full wave arrangement for supplying rectied pulses to thearmature I2 during each half cycle of the wave from a single phasesource connected to the primary coil 4Q of the transformer 4! having thesecondary coils 42 and 43. It will be seen that Fig. 3 is made up of apair of systems similar to that shown in Fig. l, with the exception thata single D. C. motor is connected in place of the separate C. motorsthat would ce provided in two complete systems like that of Fig. l. Afurther exception is that the D. C. control coils El and of one systemare connected in series with the control coils 21 and 23 of the othersystem, these coils being in series with a single control unit il whichtakes the place of two separate control units which would be necessaryif the systems were entirely separate.

One system in Fig. 3, corresponding with the system of Fig. 1, includesthe conductors I5 and I6 connected with secondary coil 42 serving as asource of A. C. and magnetic ampliers A and B with the accompanyingrectii'iers 25, 24 and I9, 25, as shown in Fig. l. The otherV system issimilar to that just described, as shown by the same referencecharacters with a prime added thereto.

It will be noted that secondary coil 43 serves as the A. C. sourceconnected to conductors I5 and IB' and that coil 43 is connected 180degrees out of phase with respect to the connection of coil 42 withconductors I5 and I6. Coil 43 is thus poled in a direction to transmitrectied pulses to the armature I2 during the parts of the cycle whencoil 42 is not transmitting pulses to the armature. Under thesecircumstances it will be seen that a rectified pulse of current issupplied to the armature I2 during each half cycle of the A. C. Wave ascompared with Fig. 1 in which a rectied pulse is transmitted to thearmature during only one-half of each cycle. The Fig. 3 arrangementconsequently presents a balanced load to the A. C. source connected withthe primary coil 40, and also supplies a larger amount of power to themotor armature I2. The detailed operation of the Fig. 3 combinationcorresponds in its parts with that described for Fig. 1.

Fig. 4 shows a three phase transformer 60 having the primary coils 6I,6'2 and 63 connected in Y-arrangement and the separate secondary coils64, and 66 coupled respectively with primary coils 6I, 62 and 63. Fig. 4includes three systems similar to that of Fig. l. The three systems arecombined in a manner similar to that explained in connection with thecombination of the two systems in Fig. 3, the motor I2 taking the placeof three separate motors that would be provided if the systems wereseparate from each other, and the control 3| taking the place of threeseparate controls. It will be noted that the D. C. control coils 21,21', 21, 28, 28', and 28 are all in series with control 50.

Conductors I5 and I5 of a rst system, corresponding with Fig. 1, areconnected to the terminals of secondary coil 64. Conductors I5 and I6 ofa second system are connected to the terminals of the secondary coil 65,and conductors I5" and I6 of a third system are connected to theterminals of secondary coil 66. The secondary coils 64, 65 and 66 are sopoled with respect to conductors I5, I6, and I5', I6 and I5, I6"respectively that they transmit rectified pulses to the armature I2 inthe same sequence as the phase sequence of the three phase sourceconnected to the primary coils 6I, 62 and 63. As a. result of thedescribed three phase arrangement, a balanced load is presented to thethree phase source of power and a considerably larger amount of power issupplied to the armature I'2 than in the case of single phase half wavesystem, such as shown in Fig. 1. The detailed operation of the parts ofFig. 4 corresponds with that described for Fig. 1.

Fig. 5 shows a modification of the three phase transformer connectionsfor conductors I5, I6, I5', I6' and I5", I6" of Fig. 4, which may besubstituted in Fig. 4. In Fig. '5, the three phase transformer 10 hasthe primary coils 1I, 12 and 13, connected in delta arrangement to thesource of A. C. Primary coil 1I has secondary coils 14 and coupledtherewith, primary coils 12 has secondary coils 16 and 11 coupledtherewith, and primary coil 13 has secondary coils 18 and 19 coupledtherewith.

Secondary coils 14 and 11 are connected in series with each other toconductors I5 and I6, coils 16 and 18 are connected in series with eachother to conductors I5 and I6', and coils 15 and 19 are connected inseries with each other to conductors I5" and I6". The coils in each pairof series connections, just described, are so poled as to add theirvoltages in a similar sequence and to transmit rectified pulses to thearmature I2 in the same sequence as the phase sequence of the threephase power source. The connections in Fig. 5 serve to distribute theload more uniformly between the different phases of the power source.

The embodiments of the invention described above are illustrative of itsapplication for the control of the speed and direction of rotation of adirect current motor. Obviously, the invention may be used in any otherapplication where it is desired to control the magnitude and directionof a unidirectional current supplied to a load in accordance with themagnitude and direction of a much weaker control current.

I have described what I believe to be the best embodiments of myinvention. I do not wish, however, to be confined to the embodimentsshown. What I desire to cover by Letters Patent is set forth in theappended claims.

I claim:

1. In a control system responsive to a unidirectional control currentwhose direction and magnitude is determinative of the direction andmagnitude of a larger unidirectional current to be supplied to a load; apair of saturable reactors, each reactor having a control winding and apair of load windings, the reactances of the load windings being reducedby the ow of unidirectional current in the control winding; circuitmeans for applying the control current to the control windings withopposite polarity in each reactor; a separate half-wave rectifierindividually connected in series with each load winding, the polarity ofevery rectifier being such as to permit current to iiow through itsassociated load winding in the same direction in all of the loadwindings; a iirst energizing circuit adapted for connection to analternating current source and serially including one of the loadwindings of each reactor together with their two associated recti-Iiers; a second energizing circuit connected in parallel with the rstenergizing circuit serially including the other load winding of eachreactor together with their two associated rectiers; and

la load supply circuit extending from a point in leach energizingcircuit intermediate the two serially connected load windings and alsointermediate the two rectifiers thereof and adapted to be connected tothe load for the controlled energization thereof.

2. A pair of control systems according to claim 1 wherein the controlcurrent is applied to each system by common circuit means, and in whichthe load supply circuit is common to the two systems, the rectifiers ineach system being so poled with respect to the alternating currentsource that the load will be energized during one series of alternatehalf-cycles of the alternating current by one of the systems, and duringthe other series of alternate half-cycles by the other system to providefull-wave energization of the load.

. 3. A plurality of control systems according to claim 1 for commonenergization from a polyphase alternating current source, consisting ofone such system for each phase, the control current being applied toeach of the several systems by common circuit means, and in which theload supply circuit is common to the several systems. the recters ineach system being so poled with respect to each phase of the alternatingcurrent source that the load will be consecutively energized by each ofthe several phases.

NHCHAEL BRACUTT.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,100,715 Jenks Nov. 30, 193'?2,310,955 Hornfeck Feb. 16, 1943 2,414,936 Edwards et al J an. 28, 19472,453,624 Glass Nov. 9, 1948 2,509,864 Hedstrom May 30, 1950

